This invention relates to display devices and particularly to display devices for indicating the condition of sensors in a vehicle.
Most automobiles include instruments for indicating the value of various measured quantities, such as the amount of fuel in the fuel tank, the engine coolant temperature, and the engine oil pressure. It is particularly important that such instruments be easily read in a short period by the vehicle operator. Conventional mechanical gauges are often difficult to read rapidly and are difficult to construct for accurate and reliable operation in an automobile environment, where they are subjected to considerable vibration over an extended operating lifetime. As a result, these instruments are generally not particularly accurate.
Published German Patent Application No. 2,242,216 discloses an electronic display apparatus for a motor vehicle which overcomes some disadvantages of mechanical displays and makes use of liquid crystal display elements embedded in the automobile windshield. In order to obtain a significant range of displayed values, a large number of such display elements is required. Another disadvantage of this prior technique is that the liquid crystal display elements are difficult to see under poor lighting conditions and therefore difficult for the driver to read when the vehicle is being operated at night.
It is therefore an object of the present invention to provide a new and improved electronic display apparatus for use in a motor vehicle.
It is a further object of the invention to provide such an apparatus which gives an accurate display of the measured quantity in a large number of value ranges with a minimum number of display elements.
It is a further object of the invention to provide such an apparatus wherein the vehicle operators' attention is easily attracted when the displayed quantity reaches a critical value.